I don't about the Australia issue, but there are a couple vendors on Ebay selling Lexus knockoffs.
At least in the states, the 17-inch wheels were available on the GS400/430 only. Most guys who want the 17's for the GS300 find takeoffs from folks who have upgraded their 400/430s with aftermarket wheels. clublexus.com always has a few people selling theirs. Again, I don't now what issues you have with getting stuff to Australia.
Personally, the Lexus wheels are Okay, but nothing to write home about. If you're looking for more bang-for-the-buck, I'd go aftermarket. Or leave the
16's on the ground and go slightly wider and slightly lower-profile in a front-line tire like a Michelin Pilot Sport. You'll get 95% of the handling of the 17's and keep a better ride.
- Mark